Breadcrumb Navigation

Discovery of new liquid quantum droplets

Physicists from Stuttgart created a liquid from an ultracold atomic gas for the first time

Scientists from the University of Stuttgart within the center of integrated quantum science and
technology IQ
ST accomplished the observation of a new quantum liquid. The journal “Nature” published
these results in their recent issue.

Liquids determine our everyday life. Their properties, e.g. surface tension or the existence of
stable droplets, are well known as well as the phase transition between liquid and gas that usually
happens at ambient temperatures. But what happens if we study this phase transition at temperatures
close to the absolute zero point of -273,15 degree celsius? Do liquids or droplets exist at these
extreme conditions?

Researchers around Tilman Pfau at the center of integrated quantum science and technology IQ
ST studied this question. They cool dysprosium atoms to temperatures as low as a few
billionth of a degree above absolute zero. In these conditions, the atoms behave according to the
laws of quantum mechanics, and thus form a quantum gas.

100 million times colder und more dilute than water

Based on the results earlier this year
[1] they are able to turn this very dilute gas
into a liquid, which is a factor of 100 million times colder and more dilute than water. They have
demonstrated this transition from gas to liquid by showing that the atoms do not try to occupy the
whole volume available but assemble in the form of droplets, which they have studied using a
levitation method.

These droplets contain only a few thousand atoms. The stability and existence of these droplets
is only possible due to quantum fluctuations that result from Heisenberg’s uncertain principle.
Furthermore, their “quantumness” imposes that when these droplets become too small they fully
evaporate back into the gas phase.

The renowned journal “Nature” published these observations in their most recent issue. These
results open up a new research direction in the physics of cold atoms where the properties of this
new quantum liquid will be studied in the future.